* Fix a deadlock where a vm_page is being held PG_BUSY throgh a vm_map
relocking operation. This can deadlock against the attempt to busy
a vm_page while holding a vm_map lock.

* The solution is a bit of a hack. Currently allow the relock attempt to
timeout and force a retry of the VM fault, which unlocks and relocks
everything. This is not the best solution but the problem occurs
fairly rarely so for now it should be an acceptable workaround.